Universal lines taken from Shaping Trees written by Thomas More (6)
I believe the answer is:
utopia
'written by thomas more' is the definition.
(book by Sir Thomas More)
'universal lines taken from shaping trees' is the wordplay.
'universal' becomes 'u'.
'lines' becomes 'ry' (abbreviation for railway).
'taken from' indicates named letters should be taken away.
'shaping trees' becomes 'topiary'.
'topiary' with 'ry' taken out is 'topia'.
'u'+'topia'='UTOPIA'
(Other definitions for utopia that I've seen before include "Imagined state of perfection" , "Literally nowhere" , "Sir Thomas More's perfect country" , "Imaginary ideal place" , "More's imaginary state" .)